Effect of laparoscopic ovarian diathermy on circulating inhibin B in women with anovulatory polycystic ovary syndrome.

BACKGROUND : Laparoscopic ovarian diathermy (LOD) frequently induces ovulation in patients with polycystic ovary syndrome (PCOS). The mechanism by which this effect occurs remains largely unexplained. The aim of this study was to measure changes in inhibin B production in response to LOD to see whether this could explain the mechanism of action of LOD. METHODS : This prospective study included 50 anovulatory women with PCOS. All women underwent LOD. Blood samples were collected before and after LOD to measure plasma concentrations of inhibin B, gonadotrophins and androgens. RESULTS : The pre-operative median plasma concentration of inhibin B was 110.0 pg/ml (range 19.0-567.0 pg/ml). There was a statistically significant inverse correlation (r= -0.286; P < 0.05) between body mass index (BMI) and inhibin B. Non-obese women with PCOS (BMI <or= 30 kg/m2; n=37) displayed significantly (P < 0.05) higher plasma inhibin B concentrations [122.0 pg/ml (range 19.0-567.0 pg/ml)] compared with those [51.0 pg/ml (range 27.0-201.0 pg/ml)] of obese PCOS women (BMI > 30 kg/m2; n=13). Following LOD, 39 women ovulated. No statistically significant change of inhibin B after LOD was observed in the overall group of women with PCOS or in the subgroup of non-obese PCOS women with higher pre-operative inhibin B. CONCLUSIONS : The lack of any change of inhibin B after LOD makes it unlikely that this hormone has any role to play in the mechanism of action of LOD.